IE 366 Chapter 9 Organization of Workstations Supplementary Material from: Groover, M.P. (2007). Work Systems and the Methods, Measurement, and Management of Work, Upper Saddle River, NJ: Pearson Prentice Hall, pp. 59 – 112.

IE Overview ● Work Flow ● Konz & Johnson Guidelines 1 – 3 ● Work Cell Layout ● K & J Guideline 4: Line Balancing ● K & J Guidelines 5 - 9

IE Work Flow ● Physical movement of work units through a sequence of unit operations. ● Unit operations examples – Manual operations ● Move box ● Load furniture into van ● File document into filing cabinet – Operations involving tools & equipment ● File part ● Paint trim around doorway ● Measure shaft diameter with micrometer ● Handwrite entries into ledger ● Apply adhesive ● Drill hole ● Mill slot ● Work Flow Patterns – Pure Sequential Operations – Mixed Sequential Operations

IE Pure Sequential Work Flow 1234

IE Mixed Sequential Work Flow

IE Types of Movement In a Sequential Workflow 1234 In-sequence Bypassing Backflow Repeat

IE From-To Charts Daily quantities (Q ij ) of work units moving between 5 workstations.

IE Bottlenecks ● Blocking – Upstream operations limited by rate of downstream operations. ● Starving – Downstream operations limited by rate of upstream operations. ● Reasons – Technological factors – Work allocation decisions – Human factors (ergonomic limitations) 1234 Downstream Upstream

IE Konz & Johnson Guidelines 1. Use Specialization Even Though It Sacrifices Versatility 2. Consider Group Technology 3. Consider Both Non-progressive and Progressive Assembly

IE Non-Progressive Assembly ● Advantages ● Neutral Characteristics ● Disadvantages

IE In-Class Exercise ● What are the work units in your project’s work system? ● Is the work progressive “assembly” or non- progressive? ● If non-progressive, what (if anything) would justify progressive?

IE U-Shaped Work Cell With Manual Handling

IE In-Line Work Cell

IE Loop Work Cell

IE U-Shaped Work Cell With Mechanized Handling

IE K & J Guidelines 4. Balance Flow Lines

IE 366 Line Balancing ● Determine quantity to be made and time allowed. – 20,000 units in 1,000 hours – Cycle time = 1,000 h / 20,000 units = 0.05 h / unit – Sum of element times = h ● Estimate an approximate number of stations. – ( h / unit) / (0.05 h / station) = 3.63 ≈ 4 stations – One operator at each station ● Make a trial solution by inspection (K & J). ● Or use a line balancing heuristic. ● Or use a line balancing program.

IE Line Balancing (K & J)

IE Line Balancing (K & J)

IE Balanced Line (K & J) S1 S2 S3 S4 S1 1,2 (0.05 h) S2 8,9 (0.04 h) S3 3,4,6 ( h) S4 6,7 S4 5,7,10 ( h)

IE 366 Line Balancing ● Determine quantity to be made and time allowed. – 20,000 units in 1,000 hours – Cycle time = 1,000 h / 20,000 = 0.05 h / item – Sum of element times = h ● Estimate an approximate number of stations. – ( h/item) / (0.05 h/station) = 3.63 ≈ 4 stations – One operator at each station ● Make a trial solution by inspection (K & J). ● Or use a line balancing heuristic. ● Or use a line balancing program.

IE Largest Candidate Rule Heuristic 1.Sort work elements in decreasing order of work times. 2.Assign elements to first workstation by starting at top of list and selecting first element that satisfies precedences and does not cause cycle time to be exceeded. Start back at top for more assignments. 3.When no more elements can be assigned without exceeding cycle time, proceed to next station. 4.Repeat steps 1 & 2 until all elements have been assigned.

IE Element Times and Precedence Diagram

IE Solution (Setup)

IE Solution (completed) (same as K&J)

IE Balanced Line

IE Balanced Line S1 S2 S3 S4 S1 1,2 (0.05 h) S2 5,3,8,10 ( h) S3 4,9 (0.05 h) S4 6,7 S4 6,7 ( h)

IE Konz & Johnson Guidelines 5. Minimize Material Handling Cost 6. Decouple Tasks 7. Make Several Identical Items at the Same Time 8. Combine Operations and Functions 9. Vary Environmental Stimulation Inversely with Task Stimulation

IE Checklist To Be Used With Process Charts and Flow Diagrams (1) From Work Systems, by Mikell Groover (2007) ● Questions Related to Material – What alternative materials can be used? – Could the part be purchased as a commercially available item? – Could the functions of several components be combined into one component? – Should this part be made or purchased (make/buy)? ● Questions Related to Processing Operations – What is the purpose of each processing operation? – Is the processing operation necessary? – Can operations be eliminated, combined, or simplified? – Is the operation time too high? – Could the processing operation be automated? – Where else could this be performed to reduce move distances?

IE Checklist To Be Used With Process Charts and Flow Diagrams (2) ● Questions Related to Inspection Operations – What is the purpose of the inspection operation? – Is the inspection operation necessary? – Can the inspection operation be combined with the previous processing operation? – Could 100% inspection be replaced with sampling inspection? – Could the inspection operation be automated? ● Questions Relating to Moves – How could moves be shortened or eliminated by combining or eliminating operations? – Could the items to be moved be batched to reduce trips? – Could the moves be mechanized or automated? – Could the operations sequence be changed to reduce move distances?

IE Checklist To Be Used With Process Charts and Flow Diagrams (3) ● Questions Relating to Delays – What is the reason for the delay? Can the reason be eliminated? – Is the delay avoidable? – Why can’t the next operation be started immediately? ● Questions Relating to Storage – Is the storage necessary? – Why can’t the item(s) be moved immediately to the next operation? – Can just-in-time delivery be used to eliminate storage?